A complete discharge device generally consists of a resistance component and an activation component to discharge a battery completely to less than 1.0 volt/cell before disposal of the battery. The incorporation of a complete discharge device into a lithium battery is intended to consume residual energy in the battery, thereby making the lithium non-reactive. In most jurisdictions, non-reactive lithium qualifies as non-hazardous waste for disposal purposes. In other words, without the discharge of the residual energy in the lithium battery, the lithium battery would have to be disposed in accordance with procedures for handling hazardous wastes.
As noted above, conventional complete discharge devices include various combinations of switches, activation methods, and resistors. Examples of batteries with conventional complete discharge devices are the BA-5590 (Li/S02) battery, as manufactured by Saft America, Inc. and the BA-5390 as manufactured by Ultralife Batteries, Inc. In this battery, a pair of contacts, made from spring contacts biased toward each other, and an insulating pull-tab arrangement therebetween, is used in conjunction with a resistive circuit. It is also believed that prior designs of complete discharge devices included a rigid plastic rod that was pushed into the battery to activate the discharge operation (e.g., Li/S02 cells formerly manufactured by Hawker Energy Products, Inc., now EnerSys Energy Products Inc of Warrensburg, Mo.).
There are, however, inherent disadvantages in the use of an insulating tab separating contact points; both from a manufacturing as well as a performance standpoint. If the spring loses its bias while in use, the removal of the tab would not activate the circuit. Similarly, the tab material must be resistant to deformation by the contacts, and must be resistant to movement until complete discharge is desired. A further potential problem when using a tab or material between the contacts is that during removal of the tab, residual material remains on the contacts and prevents activation of the discharge circuit.
Another problem inherent in methods of complete discharge is a lack of positive confirmation that discharge has taken place. In the example mentioned above, of failure to initiate discharge, the user would see that the tab has been pulled but will not readily know whether the discharge of the battery was actually initiated. It is desirable to maintain the same general format for the activation of the complete discharge device circuit, so that a common method of activation of the device would exist regardless of manufacturer. Accordingly the present disclosure is directed to several improvements to complete discharge device (CDD) activation circuits, and batteries employing such circuitry, while maintaining the known method of activating a CDD, by pulling a tab out of an aperture in the battery housing.